What is the cause of plasma para-aminohippuric acid (PAH) concentrations below the transport maximum (Tm), PAH?
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A. Reabsorption is not saturated B. Clearance equals inulin clearance C. Secretion rate equals PAH excretion rate D. Concentration in the renal vein is close to zero E. Concentration in the renal vein equals PAH concentration in the renal artery
Concentration in the renal vein is close to zero- at plasma concentrations that are lower than at the transport maximum (tm) for para-aminohippuric acid (pah) secretion, pah concentration in the renal vein is nearly zero because the sum of filtration plus secretion removes virtually all pah from the renal plasma. thus, the pah concentration in the renal vein is less than that in the renal artery because most of the pah entering the kidney is excreted in urine. pah clearance is greater than inulin clearance because pah is filtered and secreted; inulin is only filtered.